Endoscopes are instruments used to visually examine the interior of a patient during surgery. For example, endoscopes are used to visually examine internal organs such as the colon, bladder, and stomach, the abdominal cavity and peritoneum, joints such as the knee and elbow, and the larynx. Typically, endoscopes are inserted into the patient's body, deliver light to an object being examined, and collect the light reflected from the object. The reflected light carries visual information about the object being examined and can be used to create an image of the object.
Although the image provides useful medical information, it is also important that a surgeon can accurately determine the absolute size of features in the image.